We report the case of a patient with a history of malignant melanoma who presented to our clinic with a “new brown spot” on her heel.
A white woman in her 60s with a history of melanoma on her left back, Breslow thickness 0.40 mm, presented with a new brown spot on the left plantar heel that had developed within the past month. The new lesion was not brought to her attention during a pedicure appointment 3 weeks prior to presentation. The patient denied pain, pruritus, and bleeding associated with the lesion. She also denied changes in appetite, unexpected weight loss, lymphadenopathy, nausea, vomiting, and diarrhea. The patient had a history of multiple melanocytic nevi on the head, neck, trunk, and extremities.
Physical examination of the left plantar heel revealed a discrete, tan, asymmetrical, poorly demarcated 1.0-cm patch (Figure 1). A shave biopsy specimen was obtained (Figure 2A).
Examination of the patient's left plantar heel revealed a discrete, tan, asymmetrical, poorly demarcated 1.0-cm patch.
A, Shave biopsy specimen from the acral lesion demonstrates no significant changes (hematoxylin-eosin, original magnification ×40). Fontana staining confirmed absence of melanin hyperpigmentation; Perls stain was nonreactive for hemosiderin; periodic acid–Schiff, Steiner, and Giemsa preparations were nonreactive for infectious microorganisms (not shown). B, Review of ex vivo dermoscopic imageobtained at the time of tissue trimming demonstrated an irregular patch of yellow-brown discoloration with slight accentuation at sweat duct openings; no parallel ridge pattern was evident.
Histopathologic examination demonstrated no significant changes on routine hematoxylin-eosin–stained sections. Fontana staining confirmed absence of melanin hyperpigmentation; Perls stain was nonreactive for hemosiderin. Periodic acid–Schiff, Steiner, and Giemsa preparations were nonreactive for infectious microorganisms. Review of an ex vivo dermoscopic image (Figure 2B) obtained at the time of tissue trimming demonstrated an irregular patch of yellow-brown discoloration with slight accentuation at sweat duct openings; no parallel ridge pattern was evident. Exogenous tissue dyeing was suggested. After further investigation, the patient reported exposure to black walnuts. We diagnosed exogenous staining by tannins from black walnuts.
Native to the Eastern United States, the black walnut tree (Juglans nigra) is used for its timber, deep stain, and edible nuts.1 To our knowledge, this case of talon d’oyer, or “walnut heel,” is the first report of exogenous black walnut stain mimicking acral lentiginous melanoma (ALM). We selected talon d’oyer to describe the findings in this patient in tribute to another melanoma mimicker, talon noir (black heel).2,3
Reports of exogenous staining mimicking ALM are rare. Lacarrubba and coworkers2 described a case attributed to black rubber sandals. A second case in a chemical industry employee was attributed to para-phenylenediamine exposure through the workboot.4
Acral lentiginous melanoma is the most common form of melanoma in the nonwhite population.3 The poor prognosis associated with ALM has been attributed to delayed diagnosis. Dermoscopy allows expeditious identification of suspect features in the differentiation of benign and potentially malignant acral lesions.3 The dermoscopic parallel ridge pattern found in ALM is the result of atypical melanocytes within the crista profunda intermedia (epidermal rete ridges).5 Oguchi et al6 found that acral melanomas exhibited pigmentation of the ridges and less within the furrows of the dermatoglyphs. Subsequent histopathologic analysis of those lesions demonstrated atypical melanocytes containing melanin granules within the crista profunda intermedia.6 Similarly, in their retrospective analysis of Japanese patients with melanocytic lesions, Saida et al5 found the parallel ridge pattern more diagnostically accurate of melanoma in situ than “irregular diffuse pigmentation.”5(p1235)
Melanocytic nevi, subcorneal hemorrhage, exogenous pigmentation, and lentiginosis and drug-induced hyperpigmentation can demonstrate a dermoscopic parallel ridge pattern.3 Benign dermoscopic attributes include a parallel furrow pattern,5 a lattice-like pattern,6 and/or the lack of disruption of the acrosyringia within the epidermal ridges.3
Our patient’s history suggested recent onset, an uncommon feature in ALM. Because we did not specifically inquire about exogenous pigment exposures, our initial evaluation failed to reveal information that may have allowed for earlier exclusion of ALM. Our case serves as a reminder to clinicians of the importance of a thorough history. Exogenous tissue dyeing should be considered in the differential diagnosis of acral pigmented lesions, particularly if the clinical history suggests the lesion is of recent onset.
Corresponding Author: Deede Y. Liu, MD, Department of Medicine (Dermatology), University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160 (firstname.lastname@example.org).
Published Online: July 30, 2014. doi:10.1001/jamadermatol.2014.567.
Conflict of Interest Disclosures: None reported
Stashak AB, Laarman R, Fraga GR, Liu DY. Exogenous Pigmentation Mimicking Acral MelanomaA Case of Talon d’Oyer. JAMA Dermatol. 2014;150(10):1117-1118. doi:10.1001/jamadermatol.2014.567