To the Editor:
We read with great interest the article entitled “Rosette Formation Within a Proliferative Nodule of an Atypical Combined Melanocytic Nevus in an Adult” by Hoang et al. 1 The authors describe a case of rosette formation in a melanocytic tumor and state that rosette formation has not been noted in melanocytic neoplasms. We would like to draw attention to the existing literature that suggests that rosette formation in malignant melanoma is rare, but not unheard of. Although rosette formation is primarily found in tumors of neuroectodermal origin and represents a kind of atavism of these tumors, some primary melanomas or their metastases as well as atypical melanocytic neoplasms that are also of neuroectodermal origin may grow in a rosette or pseudorosette-like pattern. 2,3 We illustrate this exception with our own case of metastatic melanoma in a 29-year-old female with melanoma-associated retinopathy (MAR).
She was first seen at our dermatologic clinic in 1996 with a partially pigmented nodule on her right upper arm. After excision of this nodule, histological examination identified a nodular melanoma (tumor thickness 2.0 mm, Clark level III) with a solitary satellite metastasis. Tumor cell immunostaining detected expression of S-100 and HMB-45. A simultaneously performed tumor staging located a metastasis in the right ovary that was removed surgically.
For the following 6 months she was treated in an adjuvant setting with a melanoma-specific antiidiotypic mouse antibody. In May 2000 she developed clinical signs and symptoms of MAR. Another tumor staging in October 2000 revealed evidence of lymph node metastases in her right axilla that was removed surgically. Thereafter, MAR-symptoms declined and while continuing to receive Vindesine chemotherapy she continues to remain tumor free.
During a clinical and experimental study enrolling MAR-suspect patients, serum samples of this patient were investigated by indirect immunofluorescence on sectioned human retinal tissue, and on autologous tumor tissue. Serum was used in a dilution of 1:1000, and antibody activity was visualized using FITC-conjugated goat anti-human polyvalent antibody. The satellite metastasis removed in 1996 was strongly reactive with the patient's antibodies and showed clear evidence of rosette formation (Figs. 1,2).
We submit that in cases of unclassifiable rosette formation, clinical signs of the tumor together with immunostaining with S-100, HMB-45, tyrosinase, or MART-1 may help to differentiate between melanoma and non-melanocytic neoplasms.
Claudia Pföhler, MD
Charles E. Thirkill, PhD
Wolfgang Tilgen, MD
1. Hoang MP, Rakheja D, Amirkhan RH. Rosette formation within a proliferative nodule of an atypical combined melanocytic nevus in an adult. Am J Dermatopathol 2003; 25:35–9.
2. Banerjee SS, Harris M. Morphological and immunophenotypic variations in malignant melanoma. Histopathology 2000; 36:387–402.
3. Monteagudo C, Ferrandez A, Gonzalez-Devesa M, et al. Psammomatous malignant melanoma arising in an intradermal naevus. Histopathology 2001; 39:493–7.