MKSAP Quiz: Evaluation for a changing mole

A 26-year-old woman is evaluated for a changing mole on her left lower leg. She says it is getting bigger and darker. The patient is 5 weeks pregnant. Her only medication is a prenatal vitamin. Following a physical exam, what is the most appropriate next step in management?


A 26-year-old woman is evaluated for a changing mole on her left lower leg. She says it is getting bigger and darker. The patient is 5 weeks pregnant. Her only medication is a prenatal vitamin.

On physical examination, vital signs are normal. There is an 8-mm black and gray asymmetric papule with irregular borders on her left medial calf.

Which of the following is the most appropriate next step in management?

A. Biopsy the lesion now
B. Biopsy after delivery
C. Cryotherapy
D. Provide reassurance


MKSAP Answer and Critique

The correct answer is A. Biopsy the lesion now. This content is available to MKSAP 18 subscribers as Question 61 in the Dermatology section. More information about MKSAP is available online.

The patient has a changing mole that is very suspicious for melanoma on her left leg. It needs to be biopsied promptly as not to delay the diagnosis of melanoma. The skin biopsy is an important part of the diagnostic work-up for melanoma. Ideally, an atypical pigmented lesion should be removed using an excisional biopsy, in which the entire lesion is removed. Since this is not always practical or possible, additional options are sometimes used. These include punch biopsy, in which a sample of the lesion is removed using a cylindrical blade and sent for analysis. Although this type of biopsy generally provides a sample of adequate depth, there is concern about sampling error given that the area removed may not necessarily be representative of the remainder of the lesion. Similarly, although shave biopsies are often readily available and easy to perform, this technique carries the risk of transecting the melanoma if a deep enough sample is not taken. This would result in an underestimate of the true depth of the lesion, which could have implications regarding further work-up and management.

There is no reason to delay the biopsy in a suspicious melanocytic lesion during pregnancy. Lidocaine is classified by the FDA as pregnancy category B and can be safely used as local anesthesia during pregnancy. It is controversial to use epinephrine as it is FDA classified as category C. Although no adverse events have been documented in humans, in vitro studies of human uterine arteries have shown that in high doses, epinephrine can cause spasms and reduce flow through the uterine artery. Obtaining a biopsy from a changing mole in a pregnant woman should be done promptly as not to delay the diagnosis of melanoma.

It is not appropriate to treat a highly suspicious lesion with cryotherapy. The depth of invasion (Breslow depth) of a melanoma is the most important prognostic feature and correlates most strongly with the risk of recurrence and metastasis. Destruction of a pigmented lesion removes the possibility of making a proper diagnosis and prognosis for a potential melanoma.

Providing reassurance and thereby delaying diagnosis of melanoma could result in poor prognosis for the mother and child. Malignant melanoma is the most common malignancy during pregnancy. Studies show that changes in size in nevi during pregnancy occur on the front of the body owing to the stretching of the skin as the pregnancy progresses. Nevi on other locations, such as the leg, typically do not change during pregnancy, and this development is a red flag for possible melanoma.

Key Point

  • A suspicious melanocytic lesion should be biopsied promptly during pregnancy because dermatologic surgery under local anesthesia is safe during pregnancy; a diagnosis of melanoma should not be delayed.