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Biomedical subjects

J K Chan

Publications and source records attributed to J K Chan.

At least 217 records · Page 12Linked to original sources
PubMed1992

Sinonasal small cell neoplasm developing after radiation therapy for retinoblastoma: an immunohistologic, ultrastructural, and cytogenetic study.

Patients with retinoblastoma have an increased risk of developing second primary tumors. Only a few examples of sinonasal small cell neoplasms developing after radiation therapy for retinoblastoma have been reported. We report one such case that developed 18 years after treatment for retinoblastoma. Histologic examination revealed a small, blue, round cell tumor without rosettes or cytoplasmic glycogen. Immunohistochemically, the tumor cells were positive for neuron-specific enolase, synaptophysin, and S-100 protein, but negative for epithelial and mesenchymal markers, suggesting that this was a primitive neuroectodermal tumor. Cytogenetic studies of this tumor failed to reveal the chromosome 13 abnormality typical of retinoblastoma and the t(11:22) translocation typical of the group of peripheral neuroepitheliomas.

Adult↗
PubMed1992

Ossifying pleomorphic adenoma of the maxillary antrum.

An unusual case of pleomorphic adenoma with exuberant bone formation, occurring in the maxillary antrum of a 21-year-old male and showing repeated recurrence, is reported. In contrast to the endochondral ossification in the previous reported cases of pleomorphic adenoma, direct deposition of osteoid by metaplastic myoepithelial cells is suggested to explain the bone formation. The difficulties of distinguishing this tumour from osteosarcoma during intraoperative diagnosis are discussed.

Adult↗
PubMed1992

Extranodal Rosai-Dorfman disease: an uncommon cause of persistent nodule in the ear.

A 40-year-old woman presented with a nodule over the tragus of the right ear. A biopsy was initially reported as showing non-specific inflammation. In view of the persistence of the lesion, the histological material was reviewed, leading to revision of the diagnosis to Rosai-Dorfman disease, a diagnosis further confirmed by immunoreactivity of the histiocytes for S-100 protein. This case represented the extranodal form of Rosai-Dorfman disease in the absence of lymph node involvement.

Adult↗
PubMed1992

Basaloid-squamous carcinoma of the nasal cavity.

Basaloid-squamous carcinoma is a recently characterized, aggressive tumour occurring in the hypopharynx, larynx and base of tongue. We report a unique case involving the nasal cavity of a patient with a history of radiation therapy for nasopharyngeal carcinoma, raising the possibility that basaloid-squamous carcinoma can be radiation-associated.

Aged↗
PubMed1992

Multiple myeloma with tadpolelike cells and rosette formation.

A 65-year-old man with lower back pain was found to have multiple myeloma. Unique findings in the marrow aspirate smears of this patient were tadpolelike plasma cells and cellular rosettes simulating those seen in neuroblastoma. This case documents yet another facet of the broad morphologic spectrum of neoplastic plasma cells in multiple myeloma.

Aged↗
PubMed1992

Primary vascular tumors of lymph nodes other than Kaposi's sarcoma. Analysis of 39 cases and delineation of two new entities.

Primary vascular tumors of lymph nodes other than Kaposi's sarcoma are very rare, as attested to by only a handful of case reports in the literature. Based on an analysis of 39 such cases, we could distinguish five major groups. Hemangiomas of capillary/cavernous, lobular capillary, and cellular types were composed of compact aggregates of blood-filled vessels, variable in size, that replaced the nodal architecture partly or almost completely; some appeared to have originated in the hilum or medulla. These hemangiomas either represented incidental findings in lymph nodes or were seen with solitary lymph node enlargement; the evolution was benign with no recurrence. A distinctive benign lesion occurring exclusively in inguinal lymph nodes, which we propose designating "angiomyomatous hamartoma," showed replacement of the nodal parenchyma by smooth muscle cells and fibrous tissue, in continuity with exuberant proliferation of muscular vessels in the hilum. Epithelioid vascular tumors, characterized by plump endothelial cells with dense eosinophilic cytoplasm and numerous vacuoles, exhibited a range of differentiation, from hemangioma with well-formed vascular channels (with or without tissue eosinophilia) to hemangioendotheliomas composed predominantly of cords and sheets of tumor cells lying in a hyaline-myxoid matrix. Epithelioid hemangioendothelioma was particularly likely to be mistaken for metastatic carcinoma, and local recurrence could occur. A variant, the spindle and epithelioid hemangioendothelioma, was characterized by the presence of an additional component of spindle cells. Another tumor we found, polymorphous hemangioendothelioma, is a previously uncharacterized borderline malignant vascular tumor exhibiting solid, primitive vascular and angiomatous patterns and relatively bland cytologic features. Lymphangiomas of lymph nodes usually showed simultaneous multifocal and extra-nodal involvement and were characterized by cystic endothelium-lined spaces filled predominantly with lymph fluid. It is important to recognize these primary vascular tumors of lymph nodes to avoid mistaking them for a variety of benign vasoproliferative lesions, Kaposi's sarcoma, angiosarcoma, and metastatic cancer.

Adolescent↗
PubMed1992

Angiomyofibroblastoma of the vulva. A benign neoplasm distinct from aggressive angiomyxoma.

Aggressive angiomyxoma of pelvic soft parts is a rare lesion with a high risk of recurrence. We report 10 cases of angiomyofibroblastoma, a hitherto uncharacterized benign tumor of the vulva histologically mimicking aggressive angiomyxoma. All patients had a vulval mass, often clinically diagnosed as a Bartholin's cyst. There was no recurrence after excision. The tumors were well circumscribed, measuring 0.5-12 cm in maximum dimension. They were characterized by alternating hypercellular and hypocellular edematous zones in which abundant blood vessels (predominantly of the capillary type) were irregularly distributed. Spindled, plump spindled, and oval stromal cells were aggregated around the blood vessels, sometimes forming solid compact foci, or were loosely dispersed in the hypocellular areas. Their nuclei were bland, but rare ones were enlarged and hyperchromatic in four cases. Some cells had abundant eosinophilic hyaline cytoplasm and eccentrically placed nuclei. Mitotic figures were absent or very sparse. Scattered throughout were thin, wavy strands or thick bundles of collagen. Mast cells were readily seen in eight cases. Immunohistochemically, the stromal cells were reactive for vimentin and desmin, but not cytokeratin, muscle-specific actin, alpha-smooth muscle actin, or S-100 protein. Ultrastructural studies showed well-developed rough endoplasmic reticulum, Golgi apparatus, abundant intermediate filaments, and pinocytotic vesicles in the stromal cells. Angiomyofibroblastoma can be distinguished from aggressive angiomyxoma by its circumscribed borders, much higher cellularity, more numerous blood vessels (which lack prominent hyalinization), frequent presence of plump stromal cells, minimal stromal mucin, and rarity of erythrocyte extravasation.

Adult↗
PubMed1992

Perineurioma: an uncommon soft tissue neoplasm distinct from localized hypertrophic neuropathy and neurofibroma.

Perineurial cells, which normally surround the nerve fascicles within a nerve, can be distinguished from Schwann cells by their immunoreactivity for epithelial membrane antigen (EMA) and lack of reactivity for S-100 protein. We report two cases of perineurioma, a tumor composed exclusively of perineurial cells and distinct from other nerve sheath tumors. The first case involved a deep, soft-tissue mass of the neck, and the second involved a tumor located in the infraclavicular subcutaneous tissue. Both tumors were well circumscribed. Histologically, they were hypocellular and composed of spindle cells possessing elongated nuclei and bipolar, wavy, slender, strikingly elongated cytoplasmic processes, disposed in a background of collagen in the form of short bundles and whorls. In the first case, there were frequent calcospherites and remnants of a small nerve at the periphery. The spindle cells stained for EMA but not S-100 protein, chromogranin, neuron-specific enolase or Leu-7. Ultrastructurally, they possessed long cytoplasmic processes with incomplete basal lamina and occasional pinocytotic vesicles. Axons were not identified. Review of the literature shows that genuine perineuriomas are rare, and most cases reported as such are merely examples of localized hypertrophic neuropathy, a mononeuropathy characterized by fusiform swelling of a nerve, usually in the extremities. The involved segment in localized hypertrophic neuropathy contains distended fascicles composed of whorls of perineurial cells and fibrous tissue entrapping residual axons, probably representing a hyperplastic reaction to nerve damage. The term perineurioma should be reserved for the neoplasm composed only of perineurial cells and presenting as a soft tissue tumor.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Multiclefted nuclei. A helpful feature for identification of intermediate trophoblastic cells in uterine curetting specimens.

Intermediate trophoblast is a distinct form of trophoblast, the presence of which in uterine curettings is considered a reliable indicator of intrauterine pregnancy even in the absence of chorionic villi. However, the appearance of intermediate trophoblastic cells have not been described in sufficiently specific terms to permit their reliable identification, and distinction from decidual cells can be difficult. We have noticed for some time that the intermediate trophoblastic cells often show multiple deep clefts in the nuclei, and the present study was performed to address the issue of whether this nuclear feature is reliable for their identification. We reviewed 242 uterine curettings of intrauterine pregnancy, documented by the presence of chorionic villi, and were able to find a distinct population of cells with large, hyperchromatic, multiclefted nuclei scattered in the decidua in 88% of the cases. In most instances, these cells produced a characteristic variegated pattern that was readily recognizable at low magnification. Positive immunostaining for cytokeratin (CAM 5.2) in these isolated cells within the decidua confirmed their trophoblastic nature. In contrast, multiclefted nuclei were absent in the 51 negative control cases, which included decidualized endocervical polyps (40 cases), uterine curettings from patients with tubal pregnancy (10 cases), and endometriosis with decidual change (one case). We conclude that intermediate trophoblastic cells can usually be reliably identified in curettings of intrauterine pregnancy by their characteristic nuclear multiclefting.

Cell Nucleus↗
PubMed1992

Colloid adenocarcinoma of the urethra associated with mucosal in situ carcinoma.

Adenocarcinoma is a rarity among the primary urethral carcinomas. It usually exhibits a papillary or glandular pattern and is often believed to arise from the mucosal glands. We report a unique case showing the histologic features of colloid adenocarcinoma that appears to have evolved from carcinoma in situ of the urethral epithelium.

Adenocarcinoma, Mucinous↗
PubMed1992

Myxoid change in malignant lymphoma. Pathogenetic considerations.

Myxoid change is a rare phenomenon in malignant lymphoma, and its pathogenesis is not well understood. We present a case of large B-cell lymphoma of the small bowel in which myxoid change is confined to one of the regional lymph nodes involved by lymphoma. An increase of vimentin-positive mesenchymal cells in the myxoid zones compared with the nonmyxoid areas within the lymph node and a complete lack of myxoid change in the tumor occurring in other sites of this case suggest that the myxoid stroma results from some local factors (most probably tissue edema) stimulating proliferation of fibroblasts/myofibroblasts.

Aged↗