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E-IJD CORRESPONDENCE
Year : 2016  |  Volume : 61  |  Issue : 2  |  Page : 236
Verrucous plaque on the sole of the foot: a case of missed diagnosis


1 Department of Dermatology, Venereology and Leprosy, K. S. Hegde Medical Academy, Mangalore, Karnataka, India
2 Department of Pathology, K. S. Hegde Medical Academy, Mangalore, Karnataka, India
3 Department of General Surgery, K. S. Hegde Medical Academy, Mangalore, Karnataka, India
4 Department of Dermatology, Venereology and Leprosy, Calicut Government Medical College, Calicut, Kerala, India

Date of Web Publication1-Mar-2016

Correspondence Address:
Tonita Mariola Noronha
Departments of Dermatology, Venereology and Leprosy, K. S. Hegde Medical Academy, Mangalore, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5154.177788

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How to cite this article:
Girisha BS, Noronha TM, Permi HS, Bhagwan K R, Radhika S, Fernandes MS. Verrucous plaque on the sole of the foot: a case of missed diagnosis. Indian J Dermatol 2016;61:236

How to cite this URL:
Girisha BS, Noronha TM, Permi HS, Bhagwan K R, Radhika S, Fernandes MS. Verrucous plaque on the sole of the foot: a case of missed diagnosis. Indian J Dermatol [serial online] 2016 [cited 2020 May 27];61:236. Available from: http://www.e-ijd.org/text.asp?2016/61/2/236/177788


Sir,

Cutaneous malignant melanoma (MM) is a malignant tumor arising from the epidermal melanocyte.[1] Acral lentiginous melanoma (ALM) is a subtype of melanoma that arises on the palms, soles and subungual areas. It constitutes 29–46% of melanomas in Asians as compared to the Caucasian population in whom its incidence is as low as 2–8%.[2] There is often a delay in its diagnosis and more commonly it is misdiagnosed when it presents on the plantar surface.[3]

A 54-year-old male patient, a vegetable vendor by occupation, presented with a slow-growing lesion on his left hind foot since 2 years. He complained of intermittent dull aching pain and occasional itching. He noticed a sore within the lesion 3 months ago which refused to heal. He consulted a primary care physician who treated him with topical therapy considering it as a plantar wart. Patient denied history of trauma prior to the onset of the lesion. There was no history of significant weight loss, asthenia, hemoptysis, and melena. Cutaneous examination revealed a single ill-defined, verrucous plaque measuring 5 cm × 4 cm over the heel of the left foot on the lateral aspect. Its surface showed fissuring at the lateral border. Variable pigmentation was seen over the plaque with hyperpigmentation more pronounced at the periphery of the plaque. There was a loss of dermatoglyphics at the center of the plaque. It was nontender, with induration present 1 cm around its periphery. There was a single ulcer measuring 1 cm × 1 cm, with granulation tissue on its floor seen on the lateral edge of the plaque. It did not bleed on touch [Figure 1]. Left inguinal lymph nodes were enlarged, 1–2 cm in size, firm, and nontender. Systemic examination did not reveal any abnormality. We considered a differential diagnosis of tuberculosis verrucosa cutis (TBVC), chromoblastomycosis, plantar wart, and squamous cell carcinoma (SCC).
Figure 1: Verrucous plaque on the plantar aspect of the left foot and an overlying ulcer

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An elliptical incisional biopsy was obtained. Histopathological examination revealed the presence of abundant atypical melanocytes in the basal layer. These were infiltrating the upper layers of the epidermis and the papillary dermis with an inflammatory response comprising lymphocytes and plasma cells. The tumor tissue was arranged in nodules, having spindle to oval shaped tumor cells having melanin deposition in the cytoplasm, a hyperchromatic nucleus with coarse chromatin, and some cells showed a vesicular nucleus with prominent nucleolus [Figure 2] and [Figure 3]. These features were suggestive of MM. Immunohistochemistry was positive for HMB-45 and Melan-A while it was negative for pan cytokeratin. Hence, confirming the diagnosis of MM. Ultrasonography of the left popliteal lymph nodes was suggesting a malignant change which was confirmed with fine needle aspiration cytology. The superficial inguinal and femoral canal lymph nodes did not show any features suggestive of metastasis. The serum lactate dehydrogenase levels were normal.
Figure 2: Abundant deposition of melanin with lymphocytes and plasma cells (H and E, ×100)

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Figure 3: Tumor tissue arranged in nodules with spindle to oval shaped tumor cells (H and E, ×400)

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Subsequently, he underwent a wide excision of the melanoma with 2 cm margin and popliteal block dissection. The margins of the plaque were clear of malignancy on histopathological examination. The final diagnosis was ALM on the left foot (lateral aspect) Clark's stage II, Breslow scale 3 mm and T4N1M0. Later, he was referred to the department of Oncology for adjuvant radiotherapy to the tumor bed and the left popliteal area. He has completed the therapy and comes for regular follow-up.

Invasive melanoma of the skin is the fifth most frequent site for cancer to occur in men and the sixth most frequent site in women representing approximately 5% of all newly diagnosed cancers.[2] In 1892, it was Hutchison who recognized that melanoma could arise in pigmented lesions acquired in adult life and called it senile freckle.[4]

There are various clinical subtypes of melanoma. The most common of them is the superficial spreading melanoma which accounts for almost 70% of the cutaneous MM. Nodular melanoma, lentigo maligna melanoma, ALM, desmoplastic melanoma, mucosal melanoma, nevoid melanoma, and spitzoid melanoma are the other variants.[2]

The most common site for ALM is the sole, followed by the palm and subungual locations. The initial presentation is a variable colored (brown, black, tan, or red) macule that later develops irregular borders and variegated pigmentation. The surface may have a papule or nodule which corresponds to its vertical growth phase.[1],[2] Misdiagnosis and delay in diagnosis are particularly likely in cases of amelanotic and hypomelanotic melanoma.[3]

Our patient was a middle-aged man with a verrucous plaque on his foot. Fissuring over the plaque, verrucous surface, and loss of dermatoglyphics made us to consider the clinical differential diagnosis of TBVC, chromoblastomycosis, plantar wart, and SCC. Prolonged use of keratolytic agents over the lesion and antiseptics used for cleaning the ulcer could have camouflaged the lesion contributing to the abnormal presentation. Whenever there is a nonhealing ulcer over a preexisting lesion, it must be biopsied and sent for histopathological examination as it may be a pointer for an underlying malignancy, which was the case in our patient. Histopathology was suggestive of melanoma and further confirmation with immunohistochemistry was done because of clinical misdiagnosis. Antibody HMB 45 is a relatively specific and most useful marker for melanoma cells. It is a helpful marker in frozen sections for delineating surgical margins for residual or recurrent melanoma during Mohs surgery.[5]

The sentinel lymph node is identified by lymphatic mapping for preoperative and intraoperative localization of occult nodal metastasis. It is a powerful staging and prognostic tool.[1],[2] In our case, the left popliteal lymph nodes were unnoticed clinically though the inguinal lymph nodes were enlarged. Popliteal lymph nodes showed malignant features, whereas inguinal nodes did not. The American Joint Committee for Cancer guidelines for the thickness of the tumor, the number of metastatic nodes, and metastasis site classification of melanoma is the cornerstone for the 5-year-survival in these patients.[2] Our case was in stage T4N1M0 with relatively good prognosis.

Lesions on the foot may be completely overlooked by the patient and the treating doctor. When present on the foot, ALM can be mistaken for plantar wart, deep mycoses, or cutaneous tuberculosis. Any clinico-histopathological discordance of verrucous lesions on the sole of the foot should be subjected to immunohistochemistry.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Bishop JA. Lentigos, melanocytic naevi and melanoma. In: Burns T, editor. Rook's Textbook of Dermatology. 8th ed., Vol. 3. Singapore: Wiley-Blackwell Publishing; 2007. p. 54.1-57.  Back to cited text no. 1
    
2.
Bailey EC, Sober AJ, Mihm MC, Johnson TM. Cutaneous melanoma. In: Goldsmith LA, editor. Fitzpatrick's, Dermatology in General Medicine. 8th ed., Vol. 1. New York: Mc-Graw Hill Publishers; 2012. p. 1416-44.  Back to cited text no. 2
    
3.
Scalvenzi M, Palmisano F, Costa C. Misdiagnosed, mistreated and delay diagnosed acral melanoma: The atypical presentations. J Clin Exp Dermatol Res 2012;S6:002.  Back to cited text no. 3
    
4.
McGovern VJ. The nature of melanoma. A critical review. J Cutan Pathol 1982;9:61-81.  Back to cited text no. 4
    
5.
Palit A, Inamadar AC. Immunohistochemistry: Relevance in dermatology. Indian J Dermatol 2011;56:629-40.  Back to cited text no. 5
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