The occurrence of small cell carcinoma in the urinary bladder and prostate is rare. Only a few reports on the cytological features of small cell carcinoma of the urinary bladder in the urine specimen have been documented and, moreover, the urinary cytological features of prostate small cell carcinoma have been rarely reported. In this study, we analyzed the cytological features of four cases of small cell carcinoma of the urinary bladder and prostate, and discussed the usefulness of cytological examination of urine specimen for this type of tumor. This study included two urinary bladder and two prostate small cell carcinoma cases. Analyses of the cytological features of these cases revealed the following: i) the background was mostly inflammatory and necrotic material was also occasionally observed; ii) numerous tumor cells were present in two cases, whereas only a few neoplastic cells were observed in the remaining cases; iii) the neoplastic cells were small in size, had scant cytoplasm and a high nuclear/cytoplasmic ratio, and were arranged in small clusters or occasionally as single cells; iv) the tumor cell clusters showed prominent nuclear moldings; and v) the nuclei of the neoplastic cells were round to oval in shape with finely granular chromatin containing inconspicuous nucleoli. The cytological features of small cell carcinoma in the urine specimen are characteristic. Therefore, careful observation of the urine specimen may lead to a correct diagnosis of small cell carcinoma of the urinary bladder and, moreover, cytodiagnosis of prostate small cell carcinoma may also be possible.

Myxoid adrenocortical tumors are extremely rare neoplasms with only nine adenomas and eleven carcinomas reported in the literature. They occasionally have a pseudoglandular component resembling metastatic mucinous adenocarcinoma in the adrenal gland. However the cytological features of this unusual tumor have not been previously described. We report here the first cytopathological study of a myxoid adrenocortical adenoma with a pseudoglandular component, contributing especially to the differential diagnosis from metastatic mucinous adenocarcinoma. Two major cytopathological features distinguishing myxoid adrenocortical adenoma from metastatic mucinous adenocarcinoma in the adrenal gland are: (1) the myxoid material is found only in the extracellular space, and not in the cytoplasm; and (2) nuclei are usually located in the central portion of the cytoplasm, and not compressed to the periphery. Careful observation of these cytological features and positive immunoreactivity to Melan A, alpha-inhibin and synaptophysin can lead to the correct diagnosis.

Median raphe cyst is a rare lesion located on the median raphe. The cyst wall is lined by cuboidal to columnar cells, transitional (urothelial) cells, stratified squamous cells or a mixture of these. The normal urethral mucosa and the median raphe cyst usually lack melanocytes and/or melanin pigment. However, albeit extremely rare, the presence of melanin pigment and/or melanocytes in median raphe cyst, namely pigmented median raphe cyst, has been previously reported. The current case report presents the sixth case of pigmented median raphe cyst and discusses the possible mechanism of melanocytic colonization in this tumor. A 48-year-old male presented with a nodule on the ventral surface of the penis. Histopathological study revealed that the cyst wall was covered by uniform bland cuboidal to urothelial cells. The peculiar observation was the presence of dendritic melanocytes among the epithelial cells. Therefore, a diagnosis of pigmented median raphe cyst was determined. Immunohistochemically, stem cell factor and endothelin-1 were not expressed in the epithelial cells of the cyst wall. It is well-known that melanocytes are rarely found in various non-melanocytic tumors, a phenomenon termed ‘colonization’. The mechanism by which melanocytes appear in median raphe cyst remains unclear. The present report is the first to demonstrate that melanocytic proliferation and differentiation factors, such as stem cell factor and endothelin-1, are not involved in the pigmentation of median raphe cyst. In addition, aberrant melanocytic migration may contribute to the development of this type of lesion.

Colloid carcinoma, characterized by the presence of a large amount of extracellular mucin that results in the formation of mucous lakes with a relative paucity of neoplastic glandular cells within them, is extremely rare in the uterine cervix. Herein, we report an additional case of colloid carcinoma of the cervix and discuss the immunohistochemical characteristics and histogenesis of this extremely rare tumor. A 47-year-old Japanese female without any history of carcinomas was found to have a bulky mass in the cervix. Biopsy from the cervix revealed adenocarcinoma; subsequently, total hysterectomy was performed. Histopathologic study demonstrated that columnar or cuboidal neoplastic glandular cells forming cribriform or tubular structures floated within the mucous lakes involving almost the entire layer of the cervical wall. Adenocarcinoma in situ (AIS) component was also observed. Immunohistochemically, tumor cells of the colloid carcinoma were positive for cytokeratin 7, MUC5AC, MUC6, and p16 (diffuse), but negative for cytokeratin 20, MUC2, and cdx-2. In addition, human papillomavirus 16 was detected in both colloid carcinoma and AIS components. This is the first reported case of endocervical type colloid carcinoma, and the second documented case of cervical colloid carcinoma with immunohistochemical analyses of mucin. The present case had an endocervical type AIS component, which suggests that AIS may be a precursor lesion of colloid carcinoma. Moreover, this case clearly demonstrates that the occurrence of cervical colloid carcinoma correlates with high-risk human papillomavirus.

Although a rare condition, rosette formation in malignant melanoma has been previously documented. The present study describes the second documented case of malignant melanoma with perivascular pseudorosettes. A 38-year-old male presented with a black nodule on his back. Histopathological study revealed diffuse proliferation of neoplastic cells in the dermis and subcutis. A section of the tumor (~30%) was composed of a conventional malignant melanoma component. The remaining area was comprised of medium-sized polygonal cells with slightly eosinophilic cytoplasm and small-to-medium, round nuclei. Melanin pigment was rarely observed. A noteworthy observation was the presence of perivascular pseudorosette formations, which were characterized by their radial arrangement around the blood vessels, with a perivascular, anuclear zone. Immunohistochemically, the neoplastic cells were diffusely positive for S-100 protein and Melan-A and focally positive for HMB-45. Clinicopathological analyses of cases of malignant melanoma with rosette formations revealed that the types of rosette included the Homer-Wright type (two cases), perivascular pseudorosettes (two cases) and an unclassifiable type (one case). Immunohistochemical analysis is a useful method for forming a diagnosis as Melan-A or HMB-45 are generally expressed in all cases. Rosette formation in malignant melanoma is a distinct histopathological variant and may be an under-recognized phenomenon. Therefore, its recognition is significant for obtaining an accurate diagnosis of malignant melanoma.