Patients
Thirteen consecutive patients with definite (ACR-EULAR classification criteria) or clinically suspected pSS and with clinical and/or laboratoristic and/or US findings suspicious for MALT lymphoma were referred to our institute to undergo a US evaluation of their major SGs followed by US-guided CNB. Biopsy was performed on the parotid gland in nine patients and on the submandibular gland in four cases. The final diagnoses were B cell lymphoma in 5/13, lymphoepithelial sialadenitis in 1/13, other sialadenitis (granulomatous consistent with sarcoidosis, IgG4-related disease, chronic sclerosing, diffuse chronic) in 4/13, and miscellaneous lesions in 3/13.
Equipment
US-guided CNB were performed by one radiologist with 10 years of experience in US of the major SGs and US-guided CNB of superficial lesions, using a 14-gauge semi-automatic system (Precisa 14 G, HS Hospital Service, Aprilia, Italy) with a sampling length set on 20 mm. The US equipment used was Affiniti 70 (Philips, Eindhoven, the Netherlands) equipped with a linear high-frequency transducer (L18-5 MHz). Images and cine-loops were digitally archived (Suitestensa, Ebit AET, Esaote, Genova, Italia).
Procedure
The first step is to assess if there is a US identifiable focal lesion suspicious for MALT lymphoma, or if MALT lymphoma is only clinically suspected, without a US identifiable target. Afterwards, the planning of the procedure has to be done considering the anatomy of the facial nerve.
Facial nerve anatomy
The facial nerve emerges from the skull very deeply, anteriorly to the mastoid process. Then it runs through the parotid gland in a caudo-antero-lateral direction, splitting into two main divisions: the cervico-facial and the temporo-facial branches. During its course, it crosses the retromandibular vein and the superficial temporal artery in their vertical part, running superficially to these vessels (Fig.1). Afterwards, it branches in the anterior, superficial part of the parotid gland. Therefore, the posterior, superficial part of the parotid gland is a “safety zone” for interventional procedures (Fig.2).
MALT clinically suspected, without a US identifiable target
In this clinical scenario, the purpose is to obtain enough material for pathological diagnosis, avoiding facial nerve injuries. To achieve both goals, the patient must be in a supine position, with the shoulders slightly lifted (i.e. with a pillow below the upper back). The neck must be hyperextended, turned towards the direction opposite to the side in which sampling is planned (Fig. 3). After accurate disinfection of the skin and US probe, under US guidance, a local anaesthetic (5 mL of mepivacaine chlorhydrate) has to be injected with a fine needle (23 G) in the subcutaneous tissue and in the posterior, superficial part of the parotid gland, accessing it in its caudal part and inserting the needle in caudo-cranial direction, anteriorly to the ear lobe (“safety zone”). After some minutes, a small skin incision is done with a scalpel. Through this incision, always under US guidance, the 14 G semi-automatic needle can be inserted in the parotid gland, following the same path used for local anaesthesia (Fig. 4, Fig. 5). When the biopsy needle is positioned with the sampling window within the parotid gland, sampling can be performed. The optimal number of samples is 2 to 3.
An alternative procedure in the same clinical scenario is to perform the sampling of the submandibular gland. In this case there is no concern about nerve injuries. The patient can be positioned in a way similar to the one described above, with the head completely tilted towards the direction opposite to the side in which the procedure has to be performed. The gland can be accessed from its anterior (Fig. 6) or posterior part (Fig. 7), depending on patient's cooperation and operator's preferences. Disinfection, skin incision and tissue sampling have to be performed in the same way described above, with the significant difference that there is no concern about nerve damage.
US identifiable focal lesion suspicious for MALT
In this clinical scenario, for parotid glands it is mandatory to figure what could be the relationship between the focal lesion and the presumed course of the facial nerve, as described above. For superficial lesions, the procedure is generally feasible and safe, keeping in mind to access lesions from their posterior side (ideally from the “safety zone”), with the shortest approach, and keeping the biopsy needle as superficial as possible. For deep lesions, when a safe approach can be reasonably achieved (considering the presumed relationship between the lesion and the nerve course), the procedure can be performed; on the contrary, when safety is not guaranteed, it is suggested to suspend the procedure and to discuss with the referring physician the possibility of different diagnostic strategies (i.e. FNAC). All these considerations do not apply to submandibular glands, for which there is no concern of nerve damage. For both parotid and submandibular procedures, patient positioning, disinfection, skin incision and tissue sampling have to be performed in the same way described above.