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BMJ Case Rep. 2010; 2010: bcr0120102607.
Published online 2010 October 8. doi:  10.1136/bcr.01.2010.2607
PMCID: PMC3030111
Reminder of important clinical lesson

Tattoo pigment mimicking metastatic malignant melanoma in an axillary sentinel lymph node

Abstract

The case of a 37-year-old man with a Clarkes level III, Breslow thickness 1.2 mm superficial spreading melanoma of his forearm is described. Intraoperatively, a black-pigmented ipsilateral axillary sentinel lymph node, highly suspicious for metastatic disease, was harvested. The patient had a faded tattoo in the vicinity of the malignant melanoma. Histological examination of the lymph node demonstrated normal lymphoid tissue and the presence of pigmented macrophages due to tattoo ink. Metastatic malignant melanoma was ruled out.

The importance of histological confirmation of an enlarged pigmented node before complete dissection of the regional lymph nodes is discussed. The importance of recording the presence of decorative tattoos is stressed as the tattoo pigment may clinically mimic metastatic disease in those with malignant melanoma undergoing sentinel lymph node biopsy.

Background

Sentinel lymph node biopsy is becoming more common as one of the most powerful predictors of survival and prognosis for patients with primary melanoma. If a tattoo is present in the area of the primary melanoma, the regional lymph nodes may contain tattoo pigment mimicking metastatic malignant melanoma deposits.

Case presentation

A 37-year-old, previously well Caucasian fisherman, presented with an isolated 10 mm pigmented lesion of his left medial forearm. The lesion, present for 2 years, had recently become darker in colour, developed irregular borders and become itchy. He underwent a 5 mm skin punch biopsy under local anaesthesia, which confirmed a malignant melanoma.

Wide local excision of this lesion was performed and histology revealed a 10 mm Clarkes level III, Breslow thickness 1.2 mm (T1) superficial spreading malignant melanoma. Mitotic count revealed 7 per 10 hpf but lymphovascular invasion, ulceration or satellite lesions were not noted. Closest margins were 2.3 and 3.2 mm from lateral and deep margins, respectively.

In keeping with best practice, a wider local excision of the scar and ipsilateral sentinel lymph node biopsy was planned following normal haematology, biochemistry, chest radiography and CT thorax, abdomen and pelvis staging investigations.

At surgery, 33 mBq radiotechnetium was injected in four quadrants around the primary scar. A 2-cm wide elliptical incision circumferentially around the scar and to the deep fascia of the forearm was performed. With the aid of a probe, a single radioisotope positive node was harvested from the ipsilateral medial axilla. This node was grossly enlarged, dark black in colour and grossly suspicious for metastatic melanoma. Both wounds were closed primarily and an outpatient follow-up was arranged.

Investigations

Routine bloods, chest radiograph, CT thorax, abdomen and pelvis.

Differential diagnosis

  • Solar keratosis
  • Benign dermal naevus
  • Malignant melanoma with nodal metastases.

Treatment

Melanoma-wide local excision with 2-cm clearance margins and sentinel lymph node biopsy.

Outcome and follow-up

Histology of the skin re-excision did not demonstrate any further melanocytic cells.

The sentinel lymph node measured 30 × 15 × 10 mm. Black pigmentation was evident on the cut surface. Microscopic tissue staining and immunohistochemistry for Melan A was negative for metastatic melanoma. H&E staining demonstrated preservation of normal lymphoid tissue (figure 1) and a surprising abundance of coarse black pigment within the macrophages and lymphoid sinuses (figure 2). This foreign material was confirmed as tattoo pigment with Masson's Fontana stain.

Figure 1
Black tattoo pigment within excised sentinel lymph node with preserved architecture. H&E ×10 magnification.
Figure 2
Black carbon pigment is present in the excised sentinel node lymphoid tissue sinuses. H&E ×20 magnification.

At follow-up, the patients’ wounds had healed well and a faded tattoo was noted on the medial left forearm.

Discussion

The incidence of malignant melanoma has increased over the last decades accounting for 1–2% of all cancers but 2/3 of all skin cancer deaths.1 Prognosis depends on tumour size, Clarkes level, Breslow thickness, location, ulceration and metastases.2

Sentinel lymph node biopsy with lymphoscintigraphic mapping is a minimally invasive procedure and one of the most powerful predictors of survival and prognosis for patients with primary melanoma.3

It is indicated in Breslow depth >1 mm, Clarkes level III and in males with ulcerating truncal lesions.2

Tattoo ink, which is carbon based, consists of particles averaging 40 nm in size. Initially it lies within the epidermis and dermis upon application. At 2–3 months, it confines itself to the dermal fibroblasts and over time moves to the deep dermis and surrounding connective tissue at which time it may appear blurred and faded. It eventually travels via draining lymphatics to regional lymph nodes, as in our case.4

Such nodal pigmentation can mimic metastatic melanoma and may erroneously prompt the overzealous surgeon to proceed to radical surgery of the draining area.5

It is imperative that histological diagnosis is confirmed before completion axillary dissection is considered to avoid unnecessary patient morbidity.6

On histological examination, malignant melanoma can present as a spectrum of appearances. Immunohistochemistry, where monoclonal antibodies are directed against melanocyte antigens, is particularly important in the diagnosis of malignant melanoma metastases, including lymph node involvement. It allows the differentiation of melanocytes from other non-melanocyte cell types. The most commonly used such stains are Melan A, S100 and HMB 45.7

In addition, it is prudent to seek a history of tattooing and tattoo removal in all patients with melanoma, especially in the drainage areas of the regional nodes.

In conclusion, tattoo pigment in the sentinel lymph nodes represents a clinical challenge and this case raises awareness of this problem among surgeons and pathologists treating malignant melanoma.

Learning points

[triangle]
Minimally invasive sentinel lymph node biopsy is a powerful predictor of survival and prognosis in malignant melanoma.
[triangle]
Histological confirmation of sentinel node metastatic disease is essential before embarking on regional lymph node dissection.
[triangle]
Recording the presence of tattoos is important, as part of clinical examination, especially in patients with suspected melanoma.

Footnotes

Competing interests None.

Patient consent Obtained.

References

1. Lens MB, Dawes M. Global perspectives of contemporary epidemiological trends of cutaneous malignant melanoma. Br J Dermatol 2004;150:179–85. [PubMed]
2. Balch CM, Gershenwald JE, Soong SJ, et al. Final version of 2009 AJCC melanoma staging and classification. J Clin Oncol 2009;27:6199–206. [PMC free article] [PubMed]
3. White RR, Stanley WE, Johnson JL, et al. Long-term survival in 2,505 patients with melanoma with regional lymph node metastasis. Ann Surg 2002;235:879–87. [PubMed]
4. Jack CM, Adwani A, Krishnan H. Tattoo pigment in an axillary lymph node simulating metastatic malignant melanoma. Int Semin Surg Oncol 2005;2:28. [PMC free article] [PubMed]
5. Moehrle M, Blaheta HJ, Ruck P. Tattoo pigment mimics positive sentinel lymph node in melanoma. Dermatology (Basel) 2001;203:342–4. [PubMed]
6. Friedman T, Westreich M, Mozes SN, et al. Tattoo pigment in lymph nodes mimicking metastatic malignant melanoma. Plast Reconstr Surg 2003;111:2120–2. [PubMed]
7. Clarkson KS, Sturdgess IC, Molyneux AJ. The usefulness of tyrosinase in the immunohistochemical assessment of melanocytic lesions: a comparison of the novel T31 1 antibody (anti-tyrosinase) with S-100, HMB45, and A103 (anti-melan-A). J Clin Pathol 2001;54:196–200. [PMC free article] [PubMed]

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