Clinical History: The case is that of a 25 year old white male with a history of a hairy nevus in the right upper lateral neck region since birth, and who noticed an area of nodularity and pigment change within one border. An excisional biopsy was performed.

Microscopic Description: Sections demonstrate a broad asymmetric melanocytic lesion showing a benign congenital nevus at one edge which shows maturation to the base of the biopsy specimen but from which arises a proliferation of atypical melanocytes both as single cells as well as nests along the dermal-epidermal junction. Pagetoid upward migration is prominent. The underlying papillary dermis shows coarse fibrosis, vascular proliferation, and an area consistent with apparent regression. Atypical melanocytes extend to the base of the biopsy specimen.



Discussion: A congenital melanocytic nevus refers to a nevus present at birth containing nevomelanocytes. These are generally classified according to size, with those lesions that are more than 20 cm in greatest diameter referred to as a "giant congenital melanocytic nevi", while those under 20 cm are "non-giant congenital melanocytic nevi". The lifetime incidence of developing melanoma in patients with giant congenital nevi ranges between 6.3% and 12.0%. These are typically associated with a high mortality and represent a relative risk ranging from 250 to 1,000 times than the general population of developing melanoma.

Melanomas that arise in congenital nevi generally take the form of superficial spreading type melanomas, i.e., originating at the dermal-epidermal junction. More undifferentiated patterns including a proliferation of undifferentiated "blast" cells containing little or no melanin can also be seen. Other patterns include sarcomas and neoplasms with heterologous mesenchymal elements including rhabdomyoblasts, lipoblasts, and undifferentiated spindle cell cancers.



In our case the diagnosis of melanoma is supported by the extensive single cell proliferation of atypical melanocytes along the dermal-epidermal junction along with significant pagetoid upward migration noted laterally within the biopsy specimen. The papillary dermis shows a host response of lemellar fibrosis, brisk lymphocytic infiltrate, numerous melanophages, and atypical melanocytes admixed with the inflammatory infiltrate suggestive of an invasive component of melanoma. The utility of immunoperoxidase studies, such as S100 and HMB45 in the diagnosis of melanoma, is controversial. Most melanomas express HMB45 within melanoma cells deep in the dermis while most benign nevi show maturation and decrease of HMB45 staining by nevomelanocytes with progressive descent into the dermis. In our case however, HMB45 labeled cells within the areas of regression as well as atypical cells deep within the biopsy specimen adjacent to adnexal structures. We therefore measured to the base of the deepest atypical HMB45 positive cells, assuming that these cells immunophenotype correlated with those melanoma cells within the epidermis. This lesion measured 0.92 mm, or an intermediate thickness melanoma.



The treatment of these lesions is controversial but complete excision with negative margins is the procedure of choice. The utility of lymph node dissection is not well studied in these particular cases.

Clinical History: Ten year old male presents with a 3 mm nodularity noted on his left conjuctiva. He undergoes an excisional biopsy of the eye lesion.

Microscopic Description: The mucosa and stroma contain numerous cysts ranging in size up to 200 microns in diameter having a thick chitinous wall measuring up to 5 microns. Some of the cysts contain spores that extend from the periphery of the cyst to its center with mature spores ranging in size up to 8 to 10 microns.



Discussion: Rhinosporidiosis is caused by Rhinosporidium Seeberi which is currently classified as a fungus. Though rhinosporidiosis is typically noted in the Indian subcontinent, it has been reported in virtually all countries. In the United States, approximately 50 cases have been reported in literature, and most have occurred in the southeast region of the United States. The vector for this organism is not clearly identified; however, the eyes (specifically the conjunctiva) can be affected in a significant number of cases. In the nose, the lesions resemble allergic polyps grossly and can lead to deformities as well as disruption of the nasal cartilage. The disease is typically limited to mucous membranes and generally does not disseminate to viscera.



The diagnosis is easily made with histopathologic evaluation and does not require any further special stains. Various stages of cyst formation are noted, and the cysts range in size from 10 microns to over 200 microns. The mature spores within the cysts also range in size from a few microns to 8-10 microns. These spores are typically released into the surrounding stroma through pores or rupture within the chitinous wall. These are associated with a granulomatus response and a mixed infiltrate of lymphocytes, histiocytes, and plasma cells. Chemotherapy for these lesions has been disappointing; however, spontaneous regression has been reported to occur in some cases. The treatment is typically surgical and might require several re-excisions for repeated recurrences.