Pitfalls in the diagnosis of Malignant Melanoma


by: Kim A. Mills, M.D.

The misdiagnosis of melanoma has long been a major source of malpractice risk for both clinicians and pathologists. In April of 2002, a Melanoma Risk Management Panel of dermatopathologists, was convened by The Doctors Company. Their purpose, was to devise strategies to reduce the risk of diagnostic error and/or potential patient mismanagement when dealing with melanocytic lesions by focusing on recurrent problem areas.

Ten recurrent problems were identified through their claims review process from the four year study period of 1998 through 2001:

1. Nodular melanoma misdiagnosed as nevus.
2. Failure to recognize nevoid melanoma.
3. Claims involving shave or punch biopsies.
4. Melanoma misdiagnosed as chronically inflamed nevus.
5. Melanoma misdiagnosed as Spitz nevus.
6. Unrecognized desmosplastic melanoma.
7. Melanoma presenting as a lymph node metastasis, misdiagnosed as another neoplasm.
8. Melanoma misdiagnosed as dysplastic nevus.
9. Spindle cell melanoma misdiagnosed as spindle cell squamous cell carcinoma.
10. Patients presenting with metastatic melanoma without a known primary, and a history of
      having a skin lesion removed and discarded or destroyed without microscopic examination.

Granted, most of the problem areas listed lie in the pathologic interpretation of melanocytic lesions; the caveats of, are well known to our staff of pathologists. For our clients, items 3 and 10 should be considered.

The expert panel provided a number of additional points/precautionary statements pertaining to a clinician’s involvement with patients presenting with melanocytic lesions and are summarized below.

Some managed care plans mandate referrals to large national labs because of deeply discounted prices. The pathologists employed by such labs may be reading too many slides due to productivity standards. The examination of multiple levels and use of special stains may be discouraged in such labs due to cost. The pathologists of such labs often do not know the referring physician or do not take the time to contact the client for additional clinical information that may be paramount to a correct diagnosis.

Incomplete surgical sampling of the pigmented lesion was a major cause of misdiagnoses. Excisional biopsy is recommended for all melanocytic lesions. A partial biopsy may sample a non-diagnostic area of a true melanoma. With regard to shave biopsies, absence of the deepest aspect of the lesion may result in under-diagnosing certain forms of melanoma and may not allow for acurate staging.

Any clinically atypical lesion, that is only partially biopsied, and yields a benign diagnosis, should subsequently be completely excised.

All Spitz nevi should be completely excised, regardless of patient age.

The laboratory should be informed of any melanocytic lesion that represents a recurrence at the site of a prior biopsy, and provided with the date of that original biopsy.

Nevi that are histologically diagnosed as “atypical”, “dysplastic” or “suspicious” should be completely excised with at least 5 mm margins.

Pigmented lesions should never be destroyed or discarded without pathologic evaluation.

Troxal, D. Pitfalls in the Diagnosis of Malignant Melanoma. Am J Surg Path. 2003; 27(9):1278-82.

At Pathology Laboratory, when a melanocytic lesion is suspected, all tissue is completely submitted for histologic examination, deeper sections and special stains are routinely utilized as applicable for difficult lesions. In-house second opinions are liberally sought and often involve input from multiple pathologists. Lesions of diagnostic uncertainty are referred to highly respected national experts in melanocytic pathology.