Primary cutaneous B-cell lymphoma belongs to a group of rare B-cell lymphoproliferative disorders that present in the skin and have no evidence of extracutaneous manifestation at the time of initial diagnosis³.

Primary cutaneous B-cell lymphoma has been recently described^4,5. Most of the cases present with nodules and/or tumors. Violet-red colored, flat surfaced nodules and tumors are usually surrounded with small popular lesions, mildly infiltrated plaques and/or figurate erythematous lesions. Deeply localized nodules are commonly situated on lower extremities^1,6.

With the advent of ultrasound (US) probes with high resolution, there have been great advances in the detection and evaluation of dermatological diseases and US has gained a critical role in evaluating the diseases affecting skin and subdermal tissues⁷. As a result of a case we had, we investigated the contribution of radiological imaging techniques to the diagnosis in primary cutaneous B-cell lymphoma.

In our department, we performed a US and color Doppler US (CDUS) with a 7.5MHz superficial probe and also computed tomography (CT) on this patient. On the US, on the left hip and thigh region, together with diffuse thickness and echogenicity increase of the skin and subdermal tissues there were multiple small hypoechoic nodular lesions (Figure 1a) as well as lobulated contoured lesions (Figure 1b). CDUS revealed an increased arterial blood flow rate in this region (Figure 1c). Additionally, there was a hypoechoic mass lesion of 8x6x5cm with lobulated borders on the left femoroinguinal region with subdermal localization.

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Figure 1: On US, on left hip and thigh region, together with diffuse thickness and echogenicity increase of the skin and subdermal tissues, multiple small hypoechoic nodular lesions (arrows) (a). On US, lobulated contoured lesions were delineated (arrows) (b). CDUS revealed an increased arterial blood flow rate in this region (c).

On the CT, on the region with the lesion, there was a significant degree of diffuse thickening and density increase of the skin and subdermal tissues. On the left femoroinguinal region, the hyperdense mass lesion of 8x6x5cm with lobulated contours, which was localized between subdermal tissues and muscular tissue, was evaluated as conglomerated lymphadenopathy (LAP). The skin that was neighboring the conglomerated LAP anteriorly was thickened and retracted (Figure 2). A chest CT of the case revealed mediastinal LAP. The skin biopsy that was performed reported the diagnosis as diffuse large B-cell lymphoma.

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Figure 2: On axial CT, on the region of the lesion, there were significant degree of diffuse thickening and density increase of the skin and subdermal tissues, associated with conglomerated lymphadenopathy.

Primary cutaneous diffuse large B-cell lymphoma, leg type, may show features that overlap with other lymphomas. While a variety of primary cutaneous and systemic/extracutaneous lymphomas may show similar features, the combination of clinical findings, morphology, and immunophenotype helps to distinguish this lymphoma from other diagnostic considerations, with both important prognostic and treatment implications for patients¹¹. Punch (4–6 mm), wedge-incisional, or excisional biopsies are most frequently performed for the diagnosis of primary cutaneous B-cell lymphoma³.

According to their US appearance, the lesions in non-Hodgkin lymphomas of the cutaneous kind are classified as lesions with focal and diffuse patterns. The focal pattern is described as small (0.4-1.8cm), hypoechoic and with well-defined nodules (Type I), or with multiple nodular structures with the same characteristics, which tend to form a polylobulated hypoechoic patchy area (Type II). These lesions are localized in the dermis, in the subcutaneous layer or in both. The diffuse pattern is described as homogeneous hyperechoic thickening of the dermis (Type III) or as diffuse and unhomogeneous infiltrate involving both the dermis and subcutaneous tissue (Type IV)⁷.

B cell lymphoma can demonstrate nodular and/or diffuse patterns on US. In B-cell lymphomas, solitary or few non-ulcerated regular contoured nodules are together with frequent and early neoplastic lymph node involvement⁷. Our case presented a mixture of focal and diffuse pattern findings on US and conglomerated LAP US accompanied the picture.

Although the value of CT is limited in cases at an early stage, dermal thickening and subdermal invasion are investigated by CT. In addition to cutaneous lesions, accompanying LAPs are also identified by CT^12,13. Miketic¹² in none of the 17 stage I cases, and Bass¹³ in 32 of 43 stage I patients could not identify any describable abnormality by CT. On the CT of our case, in the skin and subdermal tissue with the lesion, there was severe diffuse thickening, a density increase and conglomerated LAP in the femoroinguinal region neighboring this region. Additionally, we identified mediastinal LAP on the thoracal CT of our case.

Magnetic resonance imaging (MRI) with good resolution is clinically advantageous in primary cutaneous lymphomas. MRI can preoperatively evaluate the depth and extension of the primary or recurrent skin tumors¹⁴.

Diffuse large B-cell lymphomas are one of the main reasons for the peripheric paralysis of the cranial nerves¹⁵. Although recurrences are quite common in the clinical course, extra dermal invasion and internal organ invasion are very rare⁴. Our case did not have internal organ involvement.

The majority of studies indicate that primary cutaneous B-cell lymphoma is highly responsive to radiotherapy. Polychemotherapy should be reserved for involvement of noncontiguous anatomic sites or those with extracutaneous spread⁴. There are publications recommending a combination of chemotherapy and radiotherapy as well^3,8,10. The prognosis of primary cutaneous B-cell lymphomas is good^4,8. Diffuse large B-cell lymphoma, leg type has a poorer prognosis. The 5-year disease-specific survival rates ranged from 43% to 63% in studies^3,4.

Although high resolution US has a high sensitivity in skin lymphomas, most of the US patterns are nonspecific and can be found in other dermatological diseases as well. Therefore, the specificity of the US is very low without making a histological examination. However US can be effective in select cases such as cases with suspected lesions and skin lesions that develop following the treatment⁷. For cases at early stages, CT is of limited value^12,13.

In conclusion, for cases that are thought to be cutaneous lymphomas as a result of clinical and radiological investigations, the diagnosis should be confirmed with skin biopsy.

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11) Hristov AC. Primary cutaneous diffuse large B-cell lymphoma, leg type: diagnostic considerations. Arch Pathol Lab Med 2012; 136: 876-81.

12) Miketic LM, Chambers TP, Lembersky BC. Cutaneous T-cell lymphoma: Value of staging and determining prognosis. AJR 1993; 160: 1129-32.

13) Bass JC, Korobkin MT, Cooper KD, Kane NM, Platt JF. Cutaneous T-cell lymphoma: CT in evaluation and staging. Radiology 1993; 186: 273-8.

14) Zemtsov A, Lorig R, Ng TC, et al. Magnetic resonance imaging of cutaneous neoplasms: clinicopathologic correlation. J Dermatol Surg Oncol 1991; 17: 416-22.

15) Amo Y, Tanei R, Yonemoto K, Katsuoka K, Mori M. Diffuse large B-cell lym-phoma associated with skin, muscle and cranial nerve involvement. Eur J Dermatol 2000; 10: 306-8.