Fluorescence in Situ Hybridization (FISH) for Distinguishing Nevoid Melanomas From Mitotically Active Nevi

Gerami, Pedram; Wass, Amanda; Mafee, Mariam; Fang, Yuaquin; Pulitzer, Melissa P.; Busam, Klaus J.

The American Journal of Surgical Pathology. 33(12):1783-1788, December 2009.:

Nevoid melanoma may resemble benign compound or intradermal nevi by their silhouette and profile on low power. Higher power usually reveals nuclear atypia, confluence of cells, incomplete maturation and dermal mitotic activity. However, to some extent all of these features maybe seen in benign compound or intradermal nevi and no single criteria can be used to differentiate nevoid melanoma from a benign nevus. The distinction can be particularly problematic in nevi that show mitotic activity and we have noted a recent trend in diagnosis of melanocytic neoplasms with dermal mitosis as nevoid melanoma despite the presence of normal maturation in the dermis and lack of significant nuclear atypia. Therefore in this study we evaluated 10 nevoid melanomas, 4 of which resulted in metastasis and 10 mitotically active nevi with fluorescence in situ hybridization targeting key chromosomal loci previously shown to effectively discriminate been malignant and benign melanocytic neoplasms. All 10 nevoid melanomas showed copy number abnormalities by fluorescence in situ hybridization in either chromosome 6 or 11 while none of the 10 mitotically active nevi did. The results demonstrate that fluorescence in situ hybridization targeting key chromosomal loci on chromosomes 6 and 11 can be effective in discriminating nevoid melanomas from mitotically active nevi. Additionally, our study presents further evidence that dermal mitoses alone without other diagnostic features such as nuclear atypia and lack of maturation does not constitute sufficient evidence alone for a diagnosis of melanoma.
(C) 2009 Lippincott Williams & Wilkins, Inc.

Atypical Spitzoid melanocytic tumours in children

Am J Surg Pathol. 2009 Sep;33(9):1386-95.

Atypical spitzoid melanocytic tumors with positive sentinel lymph nodes in children and teenagers, and comparison with histologically unambiguous and lethal melanomas.

Busam KJ, Murali R, Pulitzer M, McCarthy SW, Thompson JF, Shaw HM, Brady MS, Coit DG, Dusza S, Wilmott J, Kayton M, Laquaglia M, Scolyer RA.

Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA. busamk@mskcc.org

Children and teenagers with a positive sentinel lymph node (SLN) after a prior diagnosis of an atypical spitzoid melanocytic tumor (ASMT) are usually cared for clinically in the same way as patients with melanoma. Little is known about long-term follow-up of these individuals to determine whether this practice is appropriate. To learn more about the biology of these tumors we retrospectively reviewed the clinical and pathologic findings of children and teenagers (<18 y of age at the time of diagnosis) with an ASMT, positive SLN and follow-up of at least 3 years. Their findings were compared with histologically unambiguous melanomas of children or teenagers, who had a positive SLN or died of metastatic melanoma. Eleven individuals, 6 girls and 5 boys, with primary ASMT and positive SLN were identified. The primary tumors ranged in thickness from 2.1 to 12 mm (median, 4.6 mm; mean, 5 mm). The tumor mitotic rate ranged from 1 to 10 mitoses/mm (median, 3/mm, median, 3/mm). The positive SLNs included 6 nodes with intranodal melanocytic aggregates measuring <1 mm in greatest dimension, and 5 nodes, in which the size of the melanocyte deposits was >/=1 mm. All the patients with ASMT and positive SLN remained free of disease with a median follow-up of 47 months (mean, 61 mo, range: 36 to 132 mo). In contrast, 2 of 5 patients <18 years of age with a histologically unambiguous melanoma and a positive SLN died of metastatic melanoma. The overall disease-specific mortality rate for all patients <18 years of age diagnosed with melanoma was 12%. Our findings confirm that children and teenagers with ASMTs and positive SLNs have a less aggressive clinical course than those with histologically unambiguous melanoma.

Heavily Pigmented Melanocytic lesions

Heavily Pigmented Melanocytic Lesions: A Spectrum of Lesions with a Different Prognosis

Are these lesions indeed a horse of a different color when it comes to outcomes?

Older gray horses frequently develop heavily pigmented lesions around the anus, lips, and eyelids. A human variant of malignant melanoma resembling these lesions is called "animal-type" or "equine-type melanoma." A small number of these lesions have been reported, with some authors indicating that the course is indolent compared with conventional melanoma. These authors examined the prognostic significance of the clinical and pathologic features of such lesions.
They identified 22 patients with a diagnosis of animal/equine/pigmented synthesizing melanoma or pigmented epithelioid melanocytomas from one institution. Diagnosis was unequivocal in 14 cases. Median patient age was 35. Dysplastic nevi were found in 41%; only 9% had blue nevi without evidence of Carney complex. Ulceration was unusual; 68% of the lesions were raised, and more than half were larger than 6 mm. The head, neck, trunk, and upper extremities were the most frequent sites. The median lesion depth was 2.22 mm; more than half were in the reticular dermis. Mitosis was seen in all lesions; more than one mitotic cell was found in 41%. Sentinel lymph node (SLN) biopsy samples were taken from 17 patients; eight were positive and involved more than 1% of the lymph node. These patients underwent complete lymph node excision, and only one had an additional positive nonsentinel lymph node. Lesion depth was not significantly associated with positivity, but the positive SLN patients were older. No histologic features predicted SLN involvement, distant metastasis, or death.
Comment: The differential diagnosis of a heavily pigmented melanocytic lesion is epithelioid blue nevus and animal-type melanoma. Histological overlap and wildly ranging behavior among these lesions prompts a suggestion that the term "pigmented epithelioid melanocytoma" be applied to the full spectrum of these tumors. Unlike in conventional melanoma, younger patients with heavily pigmented lesions have a lower risk for positive SLN, but with either lesion type, the low likelihood of distant metastasis confers a good prognosis for young patients. Whether dermatopathologists call heavily pigmented lesions in young patients animal-type melanoma or epithelioid melanocytomas, the evidence predicts an indolent course.
— Angelica Maria Selim, MD
Published in Journal Watch Dermatology January 22, 2010

Citation(s):

Ludgate MW et al. Animal-type melanoma: A clinical and histopathological study of 22 cases from a single institution. Br J Dermatol 2010 Jan; 162:129.