Melanocytic matricoma is a very rare adnexal tumor that recapitulates the anagen hair follicle bulb. Few cases of malignant melanocytic matricoma have been reported, thus criteria for malignant potential have not been previously reviewed. We report a case of an 81 year old male that was originally diagnosed as atypical melanocytic matricoma. The site was re-excised with a small focus of residual tumor, but all margins were negative. The re-excision site healed without complication. However, two years after the original biopsy, a new 8 mm firm nodule appeared at the re-excision site, which was subsequently diagnosed as malignant melanocytic matricoma (MMM). In the following paper we will report a new case of MMM and review potential criteria that could be used in the future to establish malignant potential.
Melanocytic matricoma is a rare cutaneous neoplasm that typically presents clinically as a pigmented papule on sun exposed skin in the elderly [
An 81-year old white male with history of multiple non-melanoma skin cancers presented for a bothersome lesion on the posterior left forearm. Clinical suspicion was high for basal cell carcinoma and a shave biopsy was obtained. The biopsy was reviewed by a private practice dermatopathologist and was diagnosed as atypical melanocytic matricoma with positive deep margins. The site was re-excised with a small focus of remaining tumor, but with negative margins. Two years after the original biopsy, an 8 mm firm nodule appeared at the re-excision site. The new nodule was biopsied and reviewed at the University of Florida and determined to be malignant melanocytic matricoma. Histopathology of the original biopsy was compared with histopathology of the recurrent nodule. Re-excision with negative margins was performed and the re-excision site healed well. Unfortunately, the patient died several months later due to heart failure.
Microscopically, the original shave biopsy demonstrated a dermal tumor with the largest diameter measuring 2 mm, in addition to several smaller nodules (
Review of the recurrent nodule at the original biopsy site demonstrated a deep and irregular dermal nodule measuring 3 mm in diameter (
Pilomatricoma and matricoma are described as benign neoplasms consisting of
the same basic cellular components of matrical, supramatrical, and shadow or ghost cells, but with different architectural patterns [
Pilomatricoma, matricoma, and melanocytic matricoma are considered benign adnexal neoplasms [
The histological differential diagnosis of MMM includes: trichoblastoma, pigmented basal cell carcinoma, basal cell carcinoma with matrical differentiation, and most importantly, malignant melanoma [
As the number of previously described melanocytic matricomas are very small, the criteria to determine malignant potential has not been elucidated. We have compared features of all reported MMM’s, including our own (
Report | Age/Sex/Location | Follow up | Necrosis | Silhouette | Ulceration | Mitoses |
---|---|---|---|---|---|---|
Monteagudo [ | 48/M/neck | Recurrence after 2 years | Absent | Ill-defined, infiltrative | Ulcerated | 4/10 HPF |
Monteagudo [ | 77/M/chest | Unavailable | Present | Ill-defined, infiltrative | Ulcerated | 34/10 HPF |
Jani [ | 77/M/nose | Free of disease after 2 months | Present | Ill-defined, pushing | Ulcerated | Numerous |
Limarporn [ | 81/M/not reported | Unavailable | Present | Not reported | Ulcerated | 20/10 HPF |
Ardakani [ | 72/F/elbow | Free of disease after 6 months | Present | Ill-defined, pushing | Absent | 30/10 HPF |
Ardakani [ | 78/M/face | Free of disease after 6 months | Present | Ill-defined, pushing | Absent | 50/10 HPF |
Ji [ | 80/M/face | Free of disease after 1 year | Present | Ill-defined, infiltrative | Ulcerated | >10/HPF |
present report | 81/M/forearm | Recurrence after 2 years | Present | Ill-defined, infiltrative | Absent | 5/10 HPF |
In conclusion, MMM is a very rare tumor but with characteristic cytological and architectural features. Recurrence and metastasis are two definite criteria for malignancy. Multinodular infiltrative growth, tumor necrosis, and ulceration may suggest more aggressive behavior. In contrasts to previous reports, it appears that an increased number of mitoses are not a reliable predictor of behavior. Pathologists should be aware of this entity when dealing with a biphasic basaloid/melanocytic lesion to avoid misdiagnosis [
None to declare for all authors.
Nielson, C.B. and Vincek, V. (2018) Malignant Melanocytic Matricoma and Criteria for Malignancy. Open Journal of Pathology, 8, 94-100. https://doi.org/10.4236/ojpathology.2018.83011