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RESIDENT
CASE
STUDIES
October 16,
2003: Case 1 Table
of Contents | List
of Diagnoses | Case 1 | Case 2 | Case 4
48 year old female with punch biopsy.
Clinical history not provided.
Discussion by Michael Idowu, MD, and
Farrukh H. Azmi, MD, PhD
Nodular melanosis is the term given to
regressed melanoma with the presence of numerous melanophages. Partial
regression of melanoma is seen in up to one third of melanomas.
Gross Appearance: Pigmented/depigmented macular lesions which may be previously pigmented
and nodular. It may be seen in about 2% of patients with melanoma
presenting with metastatic disease in the absence of recognized primary
tumor.
Microscopic
Appearance:
- There is presence of heavy lymphocytic
infiltrate in the dermis with loss or degeneration of the tumor cells.
- There are numerous melanophages.
- Vascular fibrous tissue may be present.
- It is noteworthy to know that there may
not be melanophages in regressed melanoma, but their presence is
necessary for the regression to be called "nodular melanosis.
The initial punch biopsy in this case
showed only abundant dermal melanophages with dermal lymphocytic
infiltrate. This pattern should always make you suspicious of
regressed melanoma and you should request a re-excision.
The re-excision however showed some
residual melanocytic cells admixed with the lymphoid infiltrate. Since
the malanophages may obscure the tumor cells, it may be necessary to
bleach them.
- The residual tumor cells in the
re-excision are positive for S100.
It is important to know that this
pattern of regression is not specific for nodular melanosis, it can be
produced by solar lentigo and epithelial lesions such as basal cell
carcinoma. S100 stain mat help in differentiating these from nodular
melanosis.
Diagnostic Criteria
- Abundant dermal melanophages
- Abundant dermal lymphocytic infiltrate
- Few residual tumor cells positive for
S100
Immunostains:
Differential Diagnosis:
- Solar lentigo
- Basal cell carcinoma
- Pigment incontinence
- Insect bite
- Nevus
References:
- David Weedon: Skin Pathology. Churchill
Livingstone 2002.
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