ABSTRACT

Tattoo pigment may migrate to regional lymph nodes and appear as dense deposits and/or calcifications, mimicking malignant axillary findings on breast imaging. We report a breast imaging case with apparent axillary lymph node calcifications detected on mammography and ultrasound, in which image-guided sampling and histopathology demonstrated tattoo pigment-related deposits without malignancy. Awareness of this benign mimic, combined with careful correlation with the clinical history and multimodality imaging, can prevent unnecessary escalation of care. Additionally, confirming imaging-pathology concordance supports accurate diagnosis and helps avoid overtreatment.

Introduction

Axillary lymph node calcifications are uncommon findings on mammography and ultrasound, with a differential diagnosis that includes both benign and malignant conditions. In recent decades, the migration of tattoo pigments to regional lymph nodes has been increasingly recognized as a potential diagnostic pitfall, particularly in light of the rising prevalence of both tattoos and breast cancer screening. The first case report describing tattoo pigment mimicking mammographic calcifications was published by Honegger et al. (1) in 2004, and since then, several additional reports have documented similar findings, underscoring the challenge of distinguishing pigment deposits from true pathology (2-5). These deposits can closely resemble calcifications and, in some cases, may be mistaken for metastatic disease, creating significant diagnostic difficulties.

The aim of this case report is to raise awareness of this imaging pitfall and to emphasize the importance of correlating radiological findings with clinical history to avoid misdiagnosis and unnecessary interventions, such as biopsies. However, when clinical and radiological findings are inconclusive, histological examination may be required for a definitive diagnosis.

Case Presentation

A 50-year-old woman attended routine screening mammography. Images demonstrated hyperdense foci, simulating coarse heterogeneous calcifications, within two right axillary lymph nodes (Figure 1), which had otherwise normal size and morphology. No suspicious findings were observed in either breast. The patient was recalled for ultrasound, which confirmed the presence of echogenic foci within two lymph nodes of preserved morphology, including an intact fatty hilum and cortical thickness less than 3 mm (Figure 2). Given the absence of breast abnormalities, a contrast-enhanced breast magnetic resonance imaging (MRI) was performed to rule out occult disease. MRI revealed no suspicious breast lesions and showed magnetic susceptibility artifacts inside two right lymph nodes (Figure 3). Despite this, an ultrasound-guided core-needle biopsy was performed to exclude malignancy or extramammary metastasis (Figure 4). Radiography of the biopsy specimen confirmed the retrieval of dense material (Figure 5). Histopathology demonstrated lymphoid tissue containing greenish-black pigment deposits, with no evidence of carcinoma or calcifications (Figures 6, 7). On further clinical questioning, the patient reported a tattoo on the right arm (Figure 8), within the drainage territory of the axillary lymph nodes. Written informed consent was obtained from the patient for publication of this case and accompanying images.

Discussion and Conclusion

The presence of calcifications in the axillary lymph nodes is an unusual finding. The deposition of tattoo ink within axillary lymph nodes may mimic calcifications, as the color pigments are commonly mixed with or derived from various heavy metal oxides (6). The most widely accepted theory regarding its etiopathogenesis is that repeated intradermal injection of ink during tattooing initiates an inflammatory response driven by macrophages. These macrophages phagocytose some of the metal fragments, which are then slowly transported to the axillary lymph nodes via lymphatic vessels, where they remain for years (7). The accumulation of tattoo pigment in lymph nodes can also resemble the appearance of blue dye used for sentinel node identification, which may result in unnecessary removal of additional axillary nodes (8).

On mammography, tattoo ink deposits are usually seen as foci of calcification density within the lymph node, which may mimic true calcifications. These deposits may sometimes appear as punctate (5), coarse heterogeneous (2), which was similar to the findings in the presented case, or amorphous (3, 4) calcifications on imaging, all of which can raise suspicion of malignancy, especially in the case of a personal history of breast cancer (4) or if the lymph node shows other concerning signs, such as enlargement (1). Mammographic features suggestive of abnormal axillary lymph nodes include loss of the fatty hilum, a round rather than oval morphology, poorly defined margins, and increased size or density compared to previous imagind studies (1, 9). However, in most reported cases, lymph nodes with tattoo ink deposits have maintained normal size and morphology (3, 4).

These ink deposits can also be seen on ultrasound, usually as echogenic foci suggestive of calcifications (1). Sonography allows a better assessment of the lymph nodes. In breast cancer, axillary lymph nodes are commonly classified based on cortical morphologic features. The identification of asymmetric focal hypoechoic cortical lobulation or a completely hypoechoic lymph node should prompt cytological or histopathological evaluation (10).

There are other etiologies that can cause calcified lymphadenopathies, both benign and malignant. The benign causes include, for example, tuberculosis, sarcoidosis, histoplasmosis and prior Bacillus Calmette-Guerin vaccination. These granulomatous calcifications typically exhibit a coarse appearance (5, 11). Long-term chrysotherapy, which involves the administration of gold salts for the treatment of rheumatoid arthritis, can result in their accumulation in the lymph nodes, potentially simulating calcifications. This deposition may persist for up to 20 years after discontinuation of therapy (5, 12). A similar phenomenon occurs with certain drugs, such as cocaine, due to talc deposition. Another benign etiology to consider is fat necrosis, especially when calcifications are located in the axillary tail and the patient has a history of prior trauma (13). Talc powder from certain deodorants may also mimic calcified lymph nodes on mammography, particularly when the calcifications are bilateral (3).

The most common malignant cause of axillary lymph node calcifications is metastasis from breast carcinoma (5, 14). These calcifications are usually unilateral and present as pleomorphic and/or amorphous microcalcifications, similar to those seen in breast cancer lesions, in contrast to the coarse and large calcifications commonly associated with benign processes (14). In cases of occult carcinoma, however, axillary calcifications may be more difficult to differentiate.

Non-breast neoplasms that can occasionally cause calcified adenopathy in the axilla (often bilaterally) include those that produce mucin, such as ovarian serous-papillary adenocarcinoma (4, 9), mucinous adenocarcinoma of the colon and papillary thyroid carcinoma. These calcifications typically appear amorphous and peripheral, due to the presence of psammoma bodies (9). In addition, patients with lymphoma undergoing treatment (either chemotherapy or radiotherapy) may exhibit calcification of axillary lymphadenopathy, which, in this context, is associated with a favorable therapeutic response (5, 15).

Both clinical history and physical examination, together with imaging findings, are essential for narrowing the differential diagnoses. In cases of suspicious calcifications in axillary lymph nodes and negative results on conventional imaging (mammography/ultrasound), contrast-enhanced breast MRI may be performed to identify an occult primary tumor (16). In patients where benign status can be confidently established, unnecessary biopsies can be avoided. Nevertheless, if tissue sampling is performed, accurate clinical and radiologic-pathologic correlations are required.

In summary, the presented case report described an uncommon mammographic finding of calcification in axillary lymph nodes resulting from migration and deposition of pigment after tattooing. This condition, likely unfamiliar to most radiologists, should be considered in the differential diagnosis to avoid unnecessary escalation of care.